Certainly words of wisdom. This is a mash up of “don’t air your dirty laundry” (don’t reveal secrets publicly), “out of the closet” (a secret revealed to the public) and “skeletons in the closet” (deep secrets one does not want revealed), all referring to secrets. And of course dirty laundry often is collected in hampers in the closet so laundry and closet are word associations. On the other hand, maybe the speaker was being literal and recommending that dirty laundry in a closet will eventually make your closet smell….doubtful.